as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Recent Examples of insidious
What makes Trump's approach particularly insidious is its veneer of legality.
—
Nicholas Creel, MSNBC Newsweek, 24 July 2025
While some reasons, like the DEI rollbacks and federal job cuts, are more obvious, there are also issues that are more insidious at play.
—Janice Gassam Asare, Forbes.com, 4 Aug. 2025
Among personal vehicles manufactured in 2023, about 3 in 4 have LED headlights, the National Highway Traffic Safety Administration (NHTSA) told TIME.
Laptops, tablets, and other screens are a more insidious but constant source of LED light.
—Matt Fuchs, Time, 4 Aug. 2025
Tribalism can and does spill over into much more unpleasant areas, from basic name-calling to more insidious abuse.
—Nick Miller, New York Times, 1 Aug. 2025
See All Example Sentences for insidious
Nicholas Creel, MSNBC Newsweek, 24 July 2025
While some reasons, like the DEI rollbacks and federal job cuts, are more obvious, there are also issues that are more insidious at play.
—Janice Gassam Asare, Forbes.com, 4 Aug. 2025
Among personal vehicles manufactured in 2023, about 3 in 4 have LED headlights, the National Highway Traffic Safety Administration (NHTSA) told TIME.
Laptops, tablets, and other screens are a more insidious but constant source of LED light.
—Matt Fuchs, Time, 4 Aug. 2025
Tribalism can and does spill over into much more unpleasant areas, from basic name-calling to more insidious abuse.
—Nick Miller, New York Times, 1 Aug. 2025
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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Yet for most of the year, they are completely cut off by snow, flooding, and treacherous weather.—
David Nikel,
Forbes.com,
16 Aug. 2025
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The mountain is known for its dangerous climbing conditions, made even more treacherous because of the frequency of intense storms.—
Sam Gillette,
People.com,
14 Aug. 2025
Adjective
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There's a subtle but powerful form of manipulation happening in AI companions.—
Cornelia C. Walther,
Forbes.com,
17 Aug. 2025
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The spawn, which typically takes place over a few days and lasts less than 20 minutes, is triggered by subtle environmental cues — moon phase, tides and water temperatures — that healthy reefs once responded to in consistent synchronization.—
Ashley Miznazi,
Miami Herald,
17 Aug. 2025
Adjective
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As a part of the settlement, the false electors acknowledged their actions were used in an attempt to overturn an election.—
Jessie Opoien,
jsonline.com,
23 Aug. 2025
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It’s been a huge year for lashes: Brown and colored mascaras made a comeback, and people have been having fun with false lashes again.—
Sophia Panych,
Allure,
22 Aug. 2025
Adjective
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These emails are loaded with deceptive links that lead to malware infections, and the consequences can be severe.—
Kurt Knutsson,
FOXNews.com,
14 Aug. 2025
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The Center for Democracy and Technology, Electronic Frontier Foundation, Knight First Amendment Institute at Columbia University and American Civil Liberties Union say the software companies push deceptive marketing practices, exploit fear, normalize invasion of privacy and erode trust.—
Taylor Seely,
AZCentral.com,
13 Aug. 2025
Adjective
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Those voting for it are Sean Elo-Rivera, Jennifer Campbell, Kent Lee, Stephen Whitburn, Vivian Moreno and La Jolla’s own Joe LaCava, who has been an active supporter of this perfidious plan.—
Inga,
San Diego Union-Tribune,
16 June 2025
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Jake Gyllenhaal is his foil as the perfidious Iago, who goads Othello into unreasoning jealousy with lies about his beloved Desdemona (Molly Osborne).—
New York Times,
New York Times,
17 Feb. 2025
Adjective
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One persistent issue is hallucinations, where the AI fabricates information that may seem plausible but is factually incorrect.—
Sameer Ather,
Forbes.com,
13 Aug. 2025
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The Directors Guild of America has advised its members that the WGA’s position is incorrect, and that they may be contractually obligated to perform such activities during a strike.—
Gene Maddaus,
Variety,
12 Aug. 2025
Adjective
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One wrong step sent Luhn hurtling down the side of the mountain.—
Mitchell McCluskey,
CNN Money,
22 Aug. 2025
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Some Republicans, like Newsom rival Rep. Kiley, argue that all mid-decade redistricting – whether in Texas, California or some other state – is wrong.—
Lia Russell,
Sacbee.com,
22 Aug. 2025
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 27 Aug. 2025.
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